摘要:

Eight collections of brown trout Salmo trutta from four Lake Superior tributary systems in Wisconsin (the species' principal range in the Lake Superior drainage) were analyzed electrophoretically for enzyme expression at 15 polymorphic loci. Collections included site-specific samples from the Brule River, as well as anadromous and resident fish from the Brule and Sioux Rivers. Significant differences occurred among the eight samples at 6 of 12 possible locus comparisons (P < 0.01). Hierarchial analysis indicated that significant differences also occurred among the four drainages and among samples within drainages. Average genetic fixation values Fstindicated that the genetic variation observed among the four drainages represented approximately 1.9% of the total variation and was similar to the variation observed among samples within the Brule and Sioux drainages (1.6%). The average sample of brown trout contained about 96.5% of the genetic variation observed. Comparisons between anadromous and resident fish indicated significant genetic differences in the Brule River (P < 0.01) and nearly significant ones in the Sioux River (P < 0.07). Thus, brown trout from southwestern Lake Superior drainages appear to have a population structure organized by drainage system and by life history. Their level of stock differentiation was much less than that observed in native populations from Northern Ireland, and probably reflects the recent (1900s) introduction of brown trout to the Lake Superior watershed. Similarly, differentiation among New York State hatchery stocks was 2.2 times greater than that observed among wild Lake Superior populations. Genetic differences among Lake Superior brown trout may indicate a relatively rapid rate of population differentiation since introduction, or the partial preservation of the original genetic identifies of the different European sources that were stocked into the basin. Management actions such as stocking, regulations, and assessment should be chosen that will preserve the stock structure of brown trout in Lake Superior.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<785:SIONBT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Allelic frequencies at 27 polymorphic allozyme loci were compared among 15 collections of naturalized migratory rainbow trout Salmo gairdneri sampled from 10 stream drainages leading to Lake Superior. Multiple collections were made within the Brule River drainage in Wisconsin: one of spring-run spawning adults, one of fall-run adults, and four from Brule River tributaries. Significant allele frequency differences were observed among the 15 collections for 13 out of 21 loci examined (P < 0.05). Statistically significant differences occurred among rainbow trout from different drainages and among the four site-specific samples from Brule River tributaries. No significant differences in allelic frequencies occurred between fall-run and spring-run adult fish. Genetic fixation values Fstindicated that about 2.6% of the total genetic variation occurred among the 10 drainages and that about 2.1% occurred among the six Brule River samples. Groups of collections identified by cluster analysis of genetic distances usually contained samples that were geographically proximate, except where the number of adult spawners was believed to be less than 50. The level of population differentiation reported here for Lake Superior was less than that previously reported for native rainbow trout populations from Pacific coastal drainages or that observed for introduced brown trout resident along the south shore of Lake Superior. The spatial units of focus for management of rainbow trout in Lake Superior should be groups of geographically proximate small streams, and possibly individual large drainage systems.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<795:GCONRT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We assessed survival of wild and domestic strains of brook trout Salvelinus fontinalis embryos and yolk-sac larvae in two acidic streams, Little Laurel Run (pH 5.0–5.8) and Little Laurel Creek (pH 4.7–5.4), and a reference stream, Roaring Creek (pH 6.1–7.2), in northern West Virginia from October 1983 to May 1984. Preliminary population surveys suggested that reproductive failure due to low pH had occurred in Little Laurel Run and Little Laurel Creek. Survival rates for all developmental stages, from embryo to yolk-sac larvae, were highest at Roaring Creek and lowest at Little Laurel Creek. Survival was lowest during the hatching period at Little Laurel Run and Little Laurel Creek, where the time to the onset of hatching was less and the hatching and yolk-sac periods were greater than in Roaring Creek. In Little Laurel Run, survival after hatching was lower for the wild strain than for the domestic strain. This may have been due to extension of the hatching period for the wild strain caused by colder water temperatures. In the acidic streams, larval activity and pigmentation were reduced, and incomplete hatching was observed. These effects were most pronounced at Little Laurel Creek. Reduced survival of embryos and yolk-sac larvae may explain the low population density and altered population structure (mostly older, larger fish were present) of brook trout at Little Laurel Run and the absence of a brook trout population at Little Laurel Creek.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<807:EOLPOS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The seasonal diet and energy budget of brook trout Salvelinus fontinalis were investigated in three southern Ontario streams in 1983–1984. Stomach analyses were performed and the calculated energy value of prey items was compared with the calculated energy required for maintenance metabolism (both sets of calculations were based on literature values). Brook trout continued to feed throughout the winter, consuming a variety of prey species, especially insect larvae. Condition (weight˙length-3) declined markedly from late summer (August) to early winter (November-December) and remained low until spring (May), indicating a depletion of reserves despite the continued feeding. It appeared that low winter temperatures restricted the rate of food consumption (due perhaps to a direct effect on gastric evacuation rates) which thereby limited energy intake. This restriction is believed to be responsible for the metabolic deficit condition when minimal costs of maintenance metabolism could not be offset by energy intake. In November and December, this deficit occurred in two of six instances for immature brook trout and in four of six instances for mature brook trout. In the stream, where groundwater minimized temperature fluctuation, winter deficits only occurred in reproductively spent brook trout. Acclimatization to rapidly declining temperatures in early winter, coupled with reproductive costs for mature fish and an insufficient energy intake, resulted in the depletion of energy stores. In November-December, such a condition may limit the extent to which fish can survive unusually long winters or atypical environmental perturbations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<817:SEBOBT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The density, growth, production, and movements of juvenile coho salmon Oncorhynchus kisutch from a wild population were evaluated after the fish were transplanted into five types of habitat (clear-cut, forest, meadow, slough tributary, forest tributary) in a small southeastern Alaska stream. Instantaneous growth ranged from 0.0066 in the clear-cut habitat to 0.0055 in the slough tributary. Daily increase in fork length was about 0.10 mm/d system-wide. Annual production of coho salmon in each habitat type was: meadow, 3.32 g/m2; slough tributary, 2.47 g/m2; clear-cut, 1.75 g/m2; forest, 1.59 g/m2; and forest tributary, 1.34 g/m2. During all sampling periods, most fish were recaptured at the site where they were released; those fish that moved neither selected nor avoided specific habitat types. These findings suggest that all habitats should be managed to meet both the summer and winter needs of juvenile coho salmon because most fish do not move among habitats after the initial population adjustment in the spring. The ability of a stream to produce fish depends not only on the amount and accessibility of habitat, but also on the distribution of habitat types.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<829:SPCAHU>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A habitat suitability index (HSI) model for rock bass Ambloplites rupestris was developed from available suitability curves and field tested by comparing HSI and habitat units with seasonal standing stock, biomass, and production of rock bass in two fourth-order streams in Virginia. Consistent ranking between HSI and mean standing stocks for the study year was observed only for 250-m stream sections, the largest spatial unit of comparison. In contrast, changes in HSI explained no more than 22% of the variability in mean standing stocks in 50-m subsections of Back Creek, and were not significantly correlated with standing stocks in Little Walker Creek. Factors that apparently contributed to low correlations and ranking success included geographically homogeneous habitat and seasonal fish movements, as well as potentially important variables such as depth and cover that are not features of the tested HSI models. Annual discharge and fish distribution data further suggested that physical habitat was more limiting to populations of rock bass in the fall, not during the summer low-flow period as previously assumed. Unmeasured temporal variability in the environment may have been equally important in limiting presumed carrying capacities in study streams. Annual production for rock bass was nearly identical in both streams and averaged 1.04 g˙m-2˙year-1. This similarity in annual production was consistent with the habitat homogeneity implied by the narrow range of observed HSIs. Validation of our HSI model and similar short-term assessments of habitat quality would be more likely if study sections included the home range or annual habitat requirements of all life stages of the target species. Additional quantitative data on species-habitat relationships and systematic evaluation of individual suitability indices should also improve testing of aggregate HSI models.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<839:HSAFP>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

I examined downstream displacement of young-of-the-year fishes (primarily centrarchids and cyprinids less than 25 mm total length, TL) by field sampling of drift during floods and by an experiment conducted in a 4.9-m-long artificial stream channel. The pattern of drift during a June 1985 flood (stage increase of 3.2 m) in Brier Creek, Oklahoma, indicated that both centrarchids and cyprinids smaller than 10 mm TL were extremely susceptible to downstream displacement. Drift rates of larger fish (10–25 mm) during both the June flood and a smaller flood (stage increase of 0.4 m) in July 1985 suggested that these fishes were much less susceptible to displacement. The rapid decline in susceptibility to displacement with increase in size from the field study coincided with results obtained in the artificial channel. These results suggest that the effects of floods on stream fish communities can depend on small differences in the timing of reproduction and of flooding.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<851:SOYFTD>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Thermal responses varied among four genetic stocks of juvenile largemouth bass: northern largemouth bass Micropterus salmoides salmoides (NLMB), Florida largemouth bass M. s. floridanus (FLMB), and both reciprocal F1hybrids, NLMB ♀ x FLMB ♂ (N x F) and FLMB ♀ x NLMB ♂ (F x N). Thermal responses for each stock were measured as the critical thermal maximum, the temperature at which death occurred during a temperature increase of 0.2°C/min, for fish at various acclimation temperatures (8, 16, 24, 32°C); and chronic thermal maximum, the temperature at which death occurred during a temperature increase of 1°C/d, for fish acclimated to 32°C. The rank order of values for both response measurements was identical for the four stocks: F x N > FLMB > N x F > NLMB. Increased acclimation temperature resulted in significant, proportional increases in the critical thermal maxima for all stocks. In addition, second-generation hybrid stocks (N x F F2and F x N F2) that were acclimated at 24°C produced similar critical thermal maximum values (38.4°C and 37.8°C, respectively) that were intermediate between those of the NLMB (37.3°C) and FLMB (39.2°C). Subsequent genetic analysis revealed no correlation between critical thermal maximum and genotype at the three enzyme loci studied (Mdh-B, Idh-B, and Aat-B). Thus, the subspecific origin of the alleles at these three loci had no detectable influence on the thermal responses of hybrid offspring.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<856:CACTMO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Fecundity samples were collected in different years from three known stocks of capelin Mallotus villosus to explore regional and temporal variations in fecundity. Variation among sampling sites within the division 3L stock area, southeast of Newfoundland, was attributed to sampling error due to differences in sampling gear employed. Consequently, cast-net samples were removed from the analysis. Log-linear regressions of fecundity on length were calculated for each stock and each year. Interyear and interstock differences were tested by analysis of covariance. For all comparisons, slopes were not significantly different; however, significant differences were detected among some intercepts. Interstock differences were significant in 1985 but insignificant in 1974, 1981, and 1982. For all three capelin stocks, interyear differences were significant. Interyear differences in fecundity were not density-dependent.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<864:RATVIF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Ages of fish from three stocks of North American Arctic char Salvelinus alpinus were estimated by examination of the external surface of otoliths, burnt otolith sections, and sectioned fin rays. Anal and pectoral fins showed the best definition of opaque and translucent zones and produced similar ages. However, age estimates for both fins varied extensively from and were generally lower than ages estimated from burnt otolith sections. Age estimates from both otolith techniques were similar up to about age 8, after which burnt otolith sections yielded greater ages. Maximum ages of Alaskan fish were lower than ages of Canadian stocks from Ekalluk River and Nauyuk Lake (13, 19, and 21 years, respectively). Estimates of von Bertalanffy growth parameters from the two otolith aging techniques were different for the three stocks. Maximum ages estimated for the Alaskan and Canadian fish were similar to those presented in past studies and appear related to what has been designated the western (Alaskan) and eastern (Canadian) forms of Arctic char. We recommend that Arctic char older than about 8 years be aged by the burnt otolith section technique; a true age validation experiment remains to be conducted.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<874:EOTTTA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor